Punch press having means to change lengths of the ram



Jan. 17, 1967 H. sci-1M ET AL 3,298,267

PUNCH PRESS HAVING MEANS TO CHANGE LENGTH OF THE RAM Filed April 7, 1965 m WM/1 m 2/; W. W 0 \Mu .rllilJ. 1% z n m 1| //ZZ w 2 \A\\//AAMAMM A %27 A5; 1 t ,7 1, w w 7 m 8 ITZVTLfO/S Heinz flak SGZL'TTILIQZ AZoLS Berna? Aizi'ys.

. 5y Mm United States Patent 3,298,267 PUNCH PRESS HAVING MEANS TO CHANGE LENGTH OF THE RAM Heinrich Schmid, Glarnischstrasse, Rapperswil, Switzerland, and Alois Bernet, Rain 1995, Iona, Switzerland Filed Apr. 7, 1965, Ser. No. 446,438 Claims priority, application Switzerland, Apr. 11 1964, 4,761/ 64 8 Claims. (Cl. 83-530) This invention relates to a press having a hydraulicallyoperated ram for carrying a matrix die, a punch or other press tool, the length of the ram being adjustable.

The change in length of the ram is advantageous, because in spite of the use, for example, of various stamping tools, that is of matrices and punches of various heights, the correct approach distance between the punch and matrix die is ensured during the stamping operation.

It is known, to vary the length of the ram by mechanical means, for example by means of a screw thread.

These changes in length by mechanical means necessitate however a considerable expenditure of effort by the operator. Furthermore, adjustment by means of a screw thread can only be effected with smaller size presses, since in large size presses an excessive size of screw thread diameter must be provided. An adjustment of the ram length by mechanical means also gives rise to an excessive expenditure of time and in the case of adjustment by means of levers and rods results in a bulky construction.

The basic problem to be solved by the invention is to provide a press, in which the abovementioned disadvantages are at least partially overcome. Furthermore, the press should be simple and therefore inexpensive and also have a robust construction. The impact of the ram at the reversal of movement should be smooth, which results in vibration-free operation, so that with widely differing adjustments in length of the ram, for example, the stamping of stamped parts of high accuracy and precise surface form is ensured particularly for precision stamping.

The press according to the invention is characterised in that the press ram is divided into at least two parts which can be moved and fixed relatively to one another by hydraulic means.

Two embodiments of press rams in accordance with the invention will now be described by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIGURE 1 shows a first embodiment in longitudinal section and a control arrangement in outline; and

FIGURE 2 shows a second embodiment in longitudinal section and a control arrangement in outline.

Referring to FIGURE 1, a bush 2 is secured in the bed 1 of a precision stamping press, within which a ram consisting of two parts 3, 4 is slidable. The part 4 has a piston 5, end faces of which are subject to the action of a hydraulic medium which is admitted alternately through lines 6, 7 and which effects movement of the part 4 between abutment faces 8, 9 of the bush 2. The part 3 is slidable along the longitudinal axis of the part 4. The part 3 has a piston 53 with two end faces 11), 12 and a piston with an end face 11. The end faces 10, 11 are subject to the pressure of a hydraulic medium supplied through a line 13 and the end face 12 through a line 14. If a pressure is built up in the line 13 and the line 14 is without pressure, then the part 3 is displaced upwardly against part 4. This means that the ram 3, 4 is increased in length.

If a pressure is built up in the line 14 and the line 13 is without pressure, then the part 4 is displaced down- 3,298,267 Patented Jan. 17, 1967 wardly in relation to the part 3. This means that the ram 3, 4 is shortened. The end face 15 of the part 3 serves for carrying a matrix die (not shown). The end faces 10, 11 are separated from one another in order to provide a smaller overall construction; they can however in an embodiment not illustrated, be combined as a single end face.

The part 3 formed with a vertical dependent rod 16 carries a ring 17 at its lower end. The latter is displaceable along the rod 16 after overcoming the frictional resistance. On increasing the length of the ram 3, 4 the ring 17 on the part 4 is displaced along the rod 16. On shortening of the ram 3, 4 the rod 16 carrying along the ring 17 by the force of friction actuates a switch contact 18 arranged on the part 4 (FIGURE 1). By means of the ring 17 and the switch contact 18 compensation for leakage oil which will be explained hereinafter is effected between the chambers bounded by the end faces 10, 11.

For the control of the opposite displacement of the press ram parts 3, 4 and for locking these parts 3, 4 relatively to one another, the arrangement shown in the right-hand side of FIGURE 1 is used. A pump 19 has a suction pipe 21 leading from the tank 20 and a pressure pipe 22. From the pressure pipe 22 an excess pressure pipe 23 branches and leads back to the suction pump 21 through a drain pipe 24. The possible directions of flow in the pipes 21-24 are indicated by means of arrows. Two control devices 25, 26 have six valves 27-32. The closure members of the valves 27, 29 are permanently interconnected as shown diagrammatically in the drawing by a connecting lever, so that these valves 27, 29 are always closed or opened together. The same applies to the valves 31, 32. The valves 28, 30 have the form of non-return valves and only permit flow in the direction indicated by the arrows (FIGURE 1).

If the valve 31 and therefore also the valve 32 is opened (the valves 27, 29 are closed) then a pressure is built up in the line 13 through the pressure pipe 22 and the valve 31 in the line 14 is in communciation with the drain pipe 24 through the valve 32. On opening the valves 31, 32 and closing the valves 27, 29 the press ram 3, 4 is lengthened (FIGURE 1).

If the valve 27 and therefore also the valve 29 is open (the valves 31, 32 are closed), then a pressure is built up in the line 14 through the pressure .pipe 22 and the valve 28, and the line 13 communicates with the drain pipe 24 through the valve 29. On opening the valves 27, 29 and closing the valves 31, 32 the press ram 3, 4 is shortened (FIGURE 1).

The valves 31, 32, 27, 29 are in the closed position when the control devices 25, 26 are inoperative. The control device 25 can be operated by means of a pushbutton 33 and the control device 26 can be operated by means of a push-button 34. This means that the valves 31, 32 or 27, 29 are opened. The control device 25 can be furthermore operated by depressing the switch contact 18. This may be effected, for example, by closing an electrical circuit when the switch contact 18 is depressed by the ring 17 so that an electro-magnet in the control device 25 is energised, which opens the valves 31, 32. The connection 35 from the switch contact 18 to the control device 25 is indicated by chain line (FIGURE 1).

If both of the control devices 25, 26 are inoperative and thus the valves 31, 32 and 27, 29 are closed, then the hydraulic medium under pressure the line 13 cannot flow because of the valves 29, 30. The hydraulic medium likewise under pressure in the line 14 cannot flow because of the valves 28 and 32. On closure of the lines 13, 14 the part 3 is fixed by means of the hydraulic medium relatively to the part 4, disregarding the slight a) compressability of the hydraulic medium itself (FIG- URE 1).

The manner of operation of the adjustable press ram according to FIGURE 1 is as follows: For the adjustment of the ram height corresponding to a particular stamping tool the lowering of the part 3 in relation to the part 4 is eliected by hand by pressing the push-button 34. For raising the part 3 in relation to the part 4 the push-button 33 is pressed by hand. When the press ram 3, 4 has the correct height, the part 3 is locked floating in relation to the part 4 by hydraulic means. If there is a loss of oil from the chambers bounded by the end faces 10, 11, then the length of the press ram 3, 4 is shortened by a small amount, which means that that the ring 17 presses on the switch contact 18, where- .by the control device 25 is actuated and the valves 31, 32 are opened. Then a sulficient quantity of oil is supplied to the chambers bounded by the end faces 10, 11, to lift the ring from the switch contact 18 (FIGURE 1).

During the stamping operation the press ram 3, 4 is moved by pressure fluid alternately supplied through the pipes 6, 7. For the initiation of stamping the press ram 3, 4 is moved upwardly, and on commencement of the cutting out of a blank, the pressure rises rapidly in the hydraulic medium acting on the end faces 10, 11. As the cutting of the blank progresses the pressure on the end faces 10, 11 rises correspondingly; which means, that towards the end of the cutting process, the compression of the hydraulic rnedium increases more and more and the end of the cutting process is efiected by the resiliently rising part 3. As a result of this resilient and therefore smooth termination there is no shuddering of the stamping press, and the die can travel practically without play and plunging into the matrix edge, which ensures for precision stamping the desired surface finish and degree of precision (FIGURE 1).

In FIGURE 2 the press ram consists of the parts 36, 37. The part 36 is slidable in the cylinder 38, a piston 39 of the part 36 being actuated for raising and lowering the press ram 36, 37 alternately from both sides. The cylinder 38 is fixed on the machine bed 1. The part 37 of the press ram is constructed as a cylinder and the part 36 passes right through. A piston 48 guided in the part 37 has two end faces 41, 42. A switch contact 18 is secured to the part 37. A ring 44 is displac-ably but fixably mounted on a lower rod 43 of the part 36. In contrast to the ring 17 of FIGURE 1, the ring 34 can be clamped to the rod 43 by pressure oil. A switch contact 45 is secured on the cylinder 38, which is switched on contact by the cylinder 37 with the cylinder 38. The switch contact 18 depressed by the ring 44 actuates, as in FIGURE 1, the control device 25 through the connection 35, so that the valves 31, 32 are opened. On approach of cylinders 37 and 38 towards one another the switch contact 45 is actuated through a connection 46 so that the opening of the valves 31, 32 effected by depressing the switch contact 18 is discontinued and so that the valves 31, 32 are again closed (FIGURE 2).

In order to adjust the press ram 36, 37 to the correct height, as in FIGURE 1, the push-button 33 or 34 is operated. If the press ram 36, 37 is to be shortened, the part 37 must be moved upwardly towards the part 36 in FIGURE 32; this is effected by depressing the push-button 33, whereby the valves 31, 32 are opened. The hydraulic medium flows thus from the pressure pipe 22 through the valve 30, 31 through a pipe 47 and acts on the end face 41 of the piston 40. The hydraulic medium acting on the end face 42 flows through a pipe 48 through the open valve 32 into the drain pipe 24. For lengthening the press ram, which means in FIGURE 2 an increased projection of the part 36 from the cylinder 38, on contact between the two cylinders 36, 37, the push-button 34 is depressed. The pressure oil flows through the opened valve 27 through the pipe 48 and acts on the end surface 42. The oil acting on the end face 41 flows through the 4 pipe 47 through the opened valve 29 to the drain pipe 24 (FIGURE 2).

For the displacement of the parts 36, 37 relative to one another, which involves adjustment to the correct press ram length, a valve 49 is opened and a valve 50 is closed, so that the pressure oil in the ring 44 can be returned to the tank 28 through a pipe 51. The ring 44 can then be easily displaced by the rod 43. For the stamping operation the valve 49 is closed and the valve 58 is open, so that the ring 44 is clamped on the rod 43 by pressure oil. If during the stamping operation there is an oil leakage from the chamber bounding the end face 41, then the part 37 moves towards the part 36 in a downward direction (FIGURE 2) and the switch contact 18 is depressed by the ring 44. Thus the valves 31, 32 of the control device 25 are opened and the pressure oil flows through the pipe 47 until the ring 44 is again raised from the switch contact 18 (FIGURE 2).

During the stamping operation both the pipe 47, 48 are closed and the part 36 is locked relatively to the part 37 by hydraulic means. During the stamping process pressure oil is supplied alternately to the ducts 46, 47, so the lowest position of the .part 36 relatively to the cylinder 38 is determined by contact of the piston 39 on the end face 52 of the cylinder 38. The highest position of the part 36 in relation to the cylinder 38 is determined by the contact of the cylinder 37 on the cylinder 38.

An advantage of the embodiment, by way of example, according to FIGURE 2 in relation to that according to FIGURE 1 is to be seen in a simpler method of construction of the press ram. In FIGURE 1 the parts 3 and 4 have more closely fitting bearing surfaces than the parts 36, 37 of FIGURE 2, since in the latter example the cylinder 37 is not mounted within the cylinder 38. A further advantage with the press ram according to FIGURE 2 is the hydraulic shock damping on contact of the press ram in its upper position with the cylinder 38. In this uppermost position the cylinder 37 contacts the cylinder 38 and the shock is smoothly absorbed by the hydraulic fluid acting on the end face 41.

The pump 19 can, for example, be a swash-plate pump and serve for the stamping operation for simultaneously supplying the pipes 5, 6 with pressure oil.

We claim:

1. A press with a stationary frame and a hydraulicallyoperated press ram for carrying a matrix, a punch, or a press tool, the press ram being divided into at least two parts, which are adjustable for varying the length of the press ram, comprising first hydraulic means acting between the two parts of the press ram for hydraulically ad justing and hydraulically fixing them with respect to one another, second hydraulic means acting between one of said parts of the press ram and the stationary frame for moving the two parts of the press ram as a whole, and co-operating and adjustable abutment and switch means arranged on the two parts of the press ram, respectively, the switch means automatically controlling and maintaining the amount of a hydraulic medium in said first hydraulic means.

2. A press according to claim 1, in which a pressure source for the hydraulic medium is provided connected to said first hydraulic means through a valve that is biased to be normally closed, the switching means comprising a switch operated by said abutment if a portion of the hydraulic medium in the first hydraulic means is lost by leakage under the pressure of the second hydraulic means in the operation of the press, said switch being operatively connected to said valve for opening the valve to replace the lost hydraulic medium to the first hydraulic means.

3. A press according to claim 1, in which said first hydraulic means comprise a cylinder formed by a recess in one of the parts of the .press ram and a piston is provided connected to the other part, said piston dividing said cylinder into two compartments to each of which is connected a pipe for conducting the hydraulic medium,

and in which check valves are provided inserted in the pipes in such a way that they prevent flowing of the hydraulic medium out of the cylinder compartments.

4. A press according to claim 1, in which said first hydraulic means comprise a cylinder formed by a recess in one of the parts of the press ram and a piston is provided connected to the other part, said piston dividing said cylinder into two compartments to each of which is connected a pipe for conducting the hydraulic medium, and in which check valves are provided inserted in the pipes in such a way that they prevent flowing of the hydraulic medium out of the cylinder compartments, and in which a pressure source and a return pipe are provided connected with said two pipes through two pairs of valves which are biased to be normally closed, the valves of one pair being simultaneously operable by a first common actuating member for moving the two parts of the press ram to increase the length of the press ram, and the valves of the other pair being simultaneously operable by a second common actuating member for moving the two parts of the press ram to shorten the press ram,

5. A press according to claim 1, in which said first hydraulic means comprise a cylinder formed by a recess in one of the parts of the press ram and a piston is provided connected to the other part, said piston dividing said cylinder into two compartments to each of which is connected a pipe for conducting the hydraulic medium, and in which check valves are provided inserted in the pipes in such a way that they prevent flowing of the hydraulic medium out of the cylinder compartments, and in which a pressure source and a return pipe are provided connected with said two pipes through two pairs of valves which are biased to be normally closed, the valves of one pair being simultaneously operable by a first common actuating member for moving the two parts of the press ram to increase the length of the press ram, and the valves of the other pair being simultaneously operable by a second common actuating member for moving the two parts of the press ram to shorten the press ram, said switching means comprise a switch operated by said abutment if a portion of the hydraulic medium in the first hydraulic means is lost by leakage under the pressure of the second hydraulic means in the operation of the press, said switch being operatively connected to one of said actuating members, which calls for replacement of the lost hydraulic medium.

6. A press according to claim 1, in which one of the parts of the press ram comprises a longitudinal rod which slidably extends through an opening of the other part, said abutment being in the form of a ring adjustably supported on said rod, and the switch means comprising a switch arranged on said other part of the press ram.

7. A press according to claim 1, in which one of the parts of the press ram comprises a longitudinal rod which slid-ably extends through an opening of the other part, said abutment being in the form of a ring adjustably supported on said rod, and the switch means comprising a switch arranged on said other part of the press ram, said ring beinrg fixable on the rod by means of the pressure of a hydraulic medium.

8. Press with a hydraulically-operated press ram for carrying a matrix, a punch, or a press tool, the length of the press ram being adjustable, comprising a press ram divided into at least two parts to relatively move the two parts and which can be fixed. relatively to one another, a displaceable and fixable ring supported on a vertical rod of one of the parts of the said two .parts and a switch between the ring and the other press ram part through which the vertical rod passes for the control of a hydraulic medium for the two relatively movable press ram parts.

References Cited by the Examiner UNITED STATES PATENTS 2,358,826 9/1944 Purat 91-167 X 2,534,292 9/1950 Mueller 83639 X 3,111,062 11/1963 Peras 92-13 3,150,563 9/1964 Carrigan et al. 91--167 FOREIGN PATENTS 785,540 10/ 1957 Great Britain.

WILLIAM W. DYER, JR., Primary Examiner.

JAMES M. MEISTER, Examiner. 

1. A PRESS WITH A STATIONARY FRAME AND A HYDRAULICALLYOPERATED PRESS RAM FOR CARRYING A MATRIX, A PUNCH, OR A PRESS TOOL, THE PRESS RAM BEING DIVIDED INTO AT LEAST TWO PARTS, WHICH ARE ADJUSTABLE FOR VARYING THE LENGTH OF THE PRESS RAM, COMPRISING FIRST HYDRAULIC MEANS ACTING BETWEEN THE TWO PARTS OF THE PRESS RAM FOR HYDRAULICALLY ADJUSTING AND HYDRAULICALLY FIXING THEM WITH RESPECT TO ONE ANOTHER, SECOND HYDRAULIC MEANS ACTING BETWEEN ONE OF SAID PARTS OF THE PRESS RAM AND THE STATIONARY FRAME FOR MOVING THE TWO PARTS OF THE PRESS RAM AS A WHOLE, AND CO-OPERATING AND ADJUSTABLE ABUTMENT AND SWITCH MEANS ARRANGED ON THE TWO PARTS OF THE PRESS RAM, RESPECTIVELY, THE SWITCH MEANS AUTOMATICALLY CONTROLLING AND MAINTAINING THE AMOUNT OF A HYDRAULIC MEDIUM IN SAID FIRST HYDRAULIC MEANS. 